Radar wind turbine

ABSTRACT

A blade mounted radar system comprises a wind turbine having a hub and blades extending therefrom; a radar antenna configured to transmit and/or receive a radio frequency (RF) signal; and a processor in electrical communication with the radar antenna and configured to generate the RF signal for transmission and/or to process the received RF signal. The radar antenna is affixed to one of the blades of the wind turbine such that relative motion is defined between the radar antenna and a target within a line of sight of the radar antenna. The problem of the ground based radar line of sight being obscured by the wind turbine is mitigated in this setup, as radar and turbine coexist in the same structure. Improved performance and additional capability are enabled by elevated installation and vertical SAR imaging capability. Doppler capabilities are extended using known motion of the antenna relative to stationary objects.

FIELD OF THE INVENTION

This application relates generally to radar imaging systems.

BACKGROUND OF THE INVENTION

With an increased focus on green energy production in recent years, morewind turbines or windmills are being installed to harness wind energy.Many modern wind turbines include blades having lengths in the range ofabout twenty-five (25) meters (m) to about ninety-nine (99) m.Furthermore, such blades are rotatably mounted on a mast whose heightmay range from about eighty (80) m to about one hundred and twenty (120)m. During conditions where sufficient wind is present to turn theblades, the blades rotate a turbine attached to an electric generator tocreate electrical power. This power may be used to supply additionalelectric power to the distribution grid, or may be used directly by thewind turbine owner. As the demand for renewable energy sourcesincreases, the need for a greater number of wind turbines will increase.Multiple wind turbines are sometimes installed across expansive openareas grouped in wind farms to harness the power of the wind and convertit to electrical energy.

Ground based radars are a primary source of information regardingatmospheric conditions, location and quantity of water and/or ice, aswell as other objects in the atmosphere. Existing ground based radarapplications must meet certain criteria such as coverage, accuracy,latency, scan rate, reliability and resolution. Currently, ground basedradars serve as a key component of national surveillance systems thatdetect and track objects operating in the nation's airspace. In additionto applications in the defense industry, radar fulfills various civilianrequirements. These civilian applications include but are not limited toair traffic control, weather surveillance and tracking, trackingairborne releases of toxic materials, calibration of satellite-basedinstruments, observing debris flow from disasters such as mudslides andfloods, monitoring air quality, monitoring movement of volcanic ash, anddetecting birds and other aviation hazards.

Radar operates within its line of sight. Electromagnetic radio frequencywaves are transmitted by a radar sensor configured to transmit andreceive the electromagnetic waves. The waves propagate through the airuntil they contact an object. When the waves are impinged by an object,the waves are reflected back toward the transmission source. The radarsensor receives the reflected echo waves. Based on the time it takes forthe wave to travel to the object and be reflected back to the sensor,the round trip time of the wave may be calculated based on the speed ofthe electromagnetic wave, which is substantially equal to the speed oflight.

Doppler radar is used to detect objects which are moving with respect tothe object's background. For example, Doppler radar is effective fortracking storm systems as they move across a terrain. Doppler radardetermines the range and velocity of a target object based on theDoppler effect. As the electromagnetic waves of the radar impinge amoving target, the frequency of the echo (reflected) wave is alteredbased on the object's direction and speed of motion. For example, anobject approaching a radar sensor generates a reflected wave at afrequency higher than that of the transmitted wave. An object movingaway from the radar sensor generates a reflected wave at a frequencylower than the transmitted wave.

Wind turbines interfere with radar, particularly Doppler radar becauseof the time variable signatures generated by the rotating blades. Theinterference caused by wind turbines creates blind spots in the radarcoverage when a wind turbine is installed in the line of sight of theradar installation. In the interest of national security, permission toinstall wind turbines in the line of sight of existing radarinstallations may be prohibited. Other remediation actions includeadditional processing intended to filter the wind turbine signature.However, such techniques risk corrupting the received data signal andmay increase the likelihood that a threat will go undetected.Additionally, complex processing taxes the computer's resources andtimelines available in existing legacy radar systems. Additional airtraffic rules may be implemented in areas near or above wind turbines.However, such measures do not address the situation where an airborneobject does not comply with air traffic regulations.

Improved radar systems that are not adversely affected by wind turbinesare desired.

SUMMARY

According to an aspect of the disclosure, there is disclosed awind-turbine having radomes with radar sensors installed on thewing-tips thereof. A wind-turbine radar arrangement according to oneembodiment is intended to solve various radar return problems caused bytime-variable return signatures of large wind turbines. Further, thewind-turbine may provide the power required to operate the integratedradar system. Moreover, a radar system integrated onto the wing tips ofa wind-turbine may include a complement of various operating frequenciesadapted to maximize coverage with simultaneous imaging and surveillance.Such a radar-wind turbine system may also enable ISAR (Inverse SyntheticAperture Radar)/SAR (Synthetic Aperture Radar) imaging radarcapabilities. Thus, there is disclosed a radar system comprising anantenna configured to transmit and/or receive a radio frequency (RF)signal; and a processor in electrical communication with the antenna andconfigured to generate an RF signal for transmission and/or to process areceived RF signal; wherein the antenna is mounted to a blade of a windturbine such that relative motion is defined between the antenna and atarget within a line of sight of the antenna.

According to another aspect of the disclosure, the problem of the groundbased radar line of sight being obscured by wind turbine is mitigated inembodiments disclosed herein, as radar and turbine coexist in the samestructure. The improved performance and additional capability areenabled by one or more of a) the elevated installation turbinestructures which are generally taller than radar towers; and b) verticalSAR imaging capability wherein signals are recorded at each blade-tiplocation and processed together for improved resolution. SAR imagingcapability may be achieved from the rotation of the wind turbine blade.Since the radar located on the turbine tip is tracing a substantiallycircular path as blade rotates, high resolution imagery can beconstructed.

High resolution imagery may be further extended by orienting the turbineand selecting the blade's rotation. This can be achieved via direct windpower or driven from external power when wind conditions are inadequateto drive the desired motion and steering of the wind turbine andpropeller's motion. Doppler capability is extended by using the knownmotion of the antenna relative to stationary objects, including cloudsand/or moisture that can be stationary relative to a typical stationaryantenna.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is an illustration of a wind turbine operating within the lineof sight of a radar installation;

FIG. 1B shows a radar image indicating the time varying and constantcomponents of a wind turbine signature;

FIG. 2A shows a rotationally mounted radar system mounted on a windturbine;

FIG. 2B shows a radar antenna mounted on a blade of a wind turbine inthe radar system of FIG. 2B;

FIG. 3 is an elevation view of the blade assembly of a wind turbine inthe radar system of FIG. 2B;

FIG. 4 is an illustration of relative motion between a radar sensor anda target according to an embodiment described herein;

FIG. 5 is a process diagram for operating a rotationally mounted radarsystem;

FIG. 6 is a perspective view in phantom of a wind turbine androtationally mounted radar system.

DETAILED DESCRIPTION

It is to be understood that the figures and descriptions of the presentinvention have been simplified to illustrate elements that are relevantfor a clear understanding of the present invention, while eliminating,for purposes of clarity, many other elements found in such wind turbinesystems and radar systems. However, because such elements are well knownin the art, and because they do not facilitate a better understanding ofthe present invention, a discussion of such elements is not providedherein. The disclosure herein is directed to all such variations andmodifications known to those skilled in the art.

Wind turbines operating within the line of sight of surveillance radarinterfere with the radar. Referring to FIG. 1A, a radar installation 101having a wind turbine 103 within its line of sight 102 is shown. Theradar installation 101 includes a tower upon which the radar processingand antenna system is installed. The radar antenna or sensor may becovered with a protective radome to shield the radar 101 from theenvironment. The radar antenna 104 transmits and receives radiofrequency (RF) electromagnetic waves in a line of sight 102 toward atarget. The target may be any object within the line of sight 102 of theradar installation 101. For example, an aircraft 119, a moving stormsystem 117, or a wind turbine 103 among other detectable objects may beidentified as potential targets. The wind turbine 103 is mounted on avertical mast 105. Mounted upon the mast 105 is a nacelle 106 whichhouses the machinery and equipment needed to run the wind turbine 103including an electric generator. The electric generator has a rotorwhich is rotated within a generator housing containing coiled conductorswhich generate electricity when the rotor is rotated within the housingcoils. The rotor is coupled to a rotating blade 107 which is turned bythe force of the wind striking the surface of the blade 107 andimparting a rotational force to the blade 107 with respect to its axis.A hub at the level of the blade 107 axis is coupled to a shaft connectedto the rotor. When the wind is inadequate to produce sufficient force toturn the wind turbine electric generator 103, the generator may be usedas a motor to turn the blade 107 using externally provided electricity(e.g. by applying an external source of electricity to the generatoroutput terminals).

Due to the rotational characteristics of the wind turbine 103, the windturbine 103 creates a variable time signature detected at radarinstallation 101. The blades 107 define a rotational direction 109 a inthe direction of the radar 101 as the blade 107 passes the topmostposition relative to the blade assembly axis, and a rotational direction109 b in a direction away from the radar 101 as the blade passes thehorizontal position and begins a downward arc towards the lowermost partof the rotational path. A Doppler radar which transmits signals thatimpinge the wind turbine 103 will detect reflections that indicate anincoming movement 111 and an outgoing movement 113 caused by therotational motion of the blades 107. Furthermore, the radar 101 willdetect a zero Doppler component of the reflected signals, due to signalsthat impinge the stationary mast 105 and are reflected back to the radar101 receiver without any Doppler effect. The resulting ambiguitiesresult in a blind spot 115 in which target objects such as anapproaching storm 117 or aircraft 119 operating in the air spaceproximal to the wind turbine 103 may go undetected by radar 101. Tomaintain the effectiveness of a national radar surveillance system, thedetrimental effects of wind turbines must be mitigated. Interference maybe identified and attempts may be made to remove them from the receivedradar signal, but the algorithms needed to perform such interferencefiltering are complex and may exceed the processing capabilities ofexisting infrastructures. Pre-emptive measures, such as more tightlyregulating airspace above wind farms, or disallowing further developmentof wind farms in locations that fall within the line of site of radarinstallations in the area have obvious negative consequences.

The wind turbine 103 may operate as a component of a wind farm,comprising a number of wind turbines 103 which are electricallyinterconnected between each other and a power grid. The power grid may,in turn, receive or provide power to other wind farms or other powersources. Other power sources may provide power through other means, suchas nuclear, hydro-electric, fossil fuels, solar and the like.

FIG. 1B shows a radar image of radar reflections created by a windturbine. At the center of the image, the zero Doppler portion of thereflection signature of the wind turbine may be seen 120. Time varyingsignatures may be seen in both the positive Doppler direction 130, and anegative Doppler direction 140, indicating relative motion between therotating blades and radar sensor. The positive Doppler signatures occurwhen the blades are rotating in a direction toward the radar sensor,while the negative Doppler signatures 140 are representative of timeswhen the blades are rotating away from the radar sensor.

Referring to FIG. 2A, a radar system 200 according to an exemplaryembodiment of a wind turbine mounted radar system is shown. Radar system200 is mounted on a wind turbine 103 and functions as an integral partof the wind turbine 103 and performs as a rotatably mounted radarsystem. The wind turbine 103 is supported by a mast 105. A nacelle 106is mounted atop mast 105. The nacelle 106 houses the internal machineryof the wind turbine 103. For example, the nacelle 106 may house anelectric generator that generates electrical power when the blades 107are rotated due to the force of the wind exerted on the blade 107surface. Additional machinery may be housed in the nacelle 106. By wayof example, motors which adjust the head of the wind turbine 103 inazimuth to position the blades 107 to face into the wind or control thepitch of the blades may be located within nacelle 106. Other controlmachinery which may be housed in the nacelle 106 includes but is notlimited to, cabling, digital controllers and processors, controlcircuitry, voltage regulators, circuit breakers and other circuits orequipment necessary for operating the wind turbine 103.

Mounted at the tip of each blade 107, a radome denoted generally as 201is installed. The radome 201 is configured and installed to beaerodynamically efficient with respect to the rotational direction ofthe blades 107. For example, radome 201 may be a radome configured forinstallation on the wing tip of an aircraft. A radar sensor 203 isinstalled within radome 201 which protects the radar sensor 203 from theforce of the wind and the elements. The radar sensor 203 transmits andreceives electromagnetic signals from the tip of the blade 107 as theblade 107 rotates. Accordingly, there is relative motion between theradar sensor 203 and a potential target as the radar sensor 203 rotatesalong with the turbine blade 107. The radar sensor 203 may be coupled tothe radar system's processing modules by a cable 205 that may be guidedthrough the interior of blade 107 under its skin. The cable 205 may berun through the blade 107 to the central hub of the blade assembly wherethe cable 205 may enter the nacelle 106 through an aperture in thenacelle 106. For example, the aperture used for allowing a torque shaftto pass from the blade assembly to the rotor of the generator housedwithin the nacelle 106 may allow the cable 205 to gain access to radarprocessing equipment in the nacelle 106.

Radar sensor 203 may be a radar sensor capable of receiving radar returnsignals which may be utilized to generate a map type display and toidentify a potential target of surveillance on the map. Further, radarsensor 203 may be configured to receive a radar return signal that maybe used for creating an imaging display of a potential target, such asan image generated by synthetic aperture radar (SAR). According toanother embodiment, radar sensor 203 may be configured to receiveDoppler radar return signals which may be used to provideweather-related information to a map display. In such an embodiment, theability to generate weather radar information provides controlinformation which is beneficial to control operation of the wind turbineitself, or within the expanded scope of a wind farm. By knowing when astorm is approaching the wind farm before the weather pattern actuallyarrives, control steps may be taken to protect the structures of thewind turbine 103. For example, propellers may be slowed or blades 107aimed to a position which protects the blades 107 and wind turbine 103from excessive winds. Furthermore, if the wind farm is in communicationwith a power grid containing other power generation sources,notification of an approaching storm, which may decrease the outputprovided by the wind farm, may be used to increase power from one ormore of the other power sources. This in turns helps to maintain arelatively stable power supply to the grid and enables local grid powerbalancing.

According to an embodiment, more than one type of radar may be used by aparticular wind turbine 103. By way of non-limiting example, a windturbine 103 may be configured to support a radar sensor 203 operating ina conventional S-band Doppler mode at a location on a first blade 107,and support a radar sensor 203 operating in a different radar band, forexample, the Ku band, which is capable of detecting wind shears, at alocation on a second blade 107 of the wind turbine. The combinedattributes of these two radar technologies provide increased warningtime of approaching weather systems. The increased warning time providestime to prepare the wind farm for defense against an impending weatherevent, and further provides the underlying grid and nearby facilitiesincreased lead time to prepare before the effects of a severe weatherevent are felt. The nearby facilities may include additional powergeneration facilities, or facilities that provide backup services to thewind farm.

Furthermore, locating near airports wind turbines having multi-moderotating radars for surveillance, weather and imaging can provideenhanced benefits such as increased power generation and better airtraffic control in adverse weather conditions.

Referring now to FIG. 3, there is shown an elevation view of a rotatingblade assembly 300 including a rotationally mounted radar system. Theblade assembly 300 includes three blades 107 mounted to a common hub303. At the tip of each blade 107, a radome 201 a, 201 b, 201 c ismounted and configured to protect a radar sensor housed within theradome 201. The radome 201 is positioned to reduce wind resistanceexerted on the radome 201 as the radome 201 rotates about thecircumferential path 301 defined by the tip of the blade 107 as theblade 107 rotates about hub 303. As each radar sensor housed withinradome 201 a, 201 b, 201 c rotates about path 301, a radar signal istransmitted by the sensor toward a target. The radar signal is impingedby the target and an echo signal is reflected from the target objectback toward the radar sensor. The echoed signals are received by theradar sensor and may be stored in memory for later processing asdescribed hereinbelow.

Referring to FIG. 4, an illustration is provided showing radar signalsof a rotationally mounted radar sensor. The radar sensor, denoted ascircles labeled A, B, C, and D, travels along a circumferential path301. For example, the circumferential path 301 is defined by therotational motion of a blade tip of a wind turbine as shown in FIG. 3.As the sensor travels about path 301 in a given rotational direction401, the sensor will be positioned at point A as some point in thesensor's rotation. As the sensor rotates, the sensor's position willchange and move along path 301 until the sensor reaches position B.Similarly, as the sensor continues its rotational motion 401, the sensorwill reach position C, and subsequently, position D.

When at position A, the radar sensor transmits a radar signal 403 in thedirection of target 419. The radar signal 403 is impinged upon by thetarget 419 and an echo signal 405 is reflected back towards the radarsensor. The returned signal echo 405 will have properties that areindicative of the nature of the target 419. These properties may includebut are not limited to, the round trip time between the transmission ofthe radar signal 403 and the reception of the echo signal 405, the phaseof the received echo signal 405, and the polarization of the receivedecho signal 405. When the radar sensor is positioned at point B, theradar sensor transmits a radar signal 407 in the direction of target419. The radar signal 407 reflects off of the target 419 and creates anecho signal 409 which is reflected back to the radar sensor. The echosignal 409 may contain properties indicative of the target 419 as viewedfrom point B. When the radar sensor is positioned at point C, the radarsensor transmits a radar signal 411 in the direction of target 419. Theradar signal 411 reflects off of the target 419 and creates an echosignal 413 which is reflected back the radar sensor. The echo signal 413may contain properties indicative of the target 419 as viewed from pointC. When the radar sensor is positioned at point D, the radar sensortransmits a radar signal 415 in the direction of target 419. The radarsignal 415 reflects off of the target 419 and creates an echo signal 417which is reflected back the radar sensor. The echo signal 417 maycontain properties indicative of the target 419 as viewed from point D.

As each echo signal 405, 409, 413, 417 is received by the radar sensor,the characteristics of the echo signal 405, 409, 413, 417 are saved in amemory for subsequent processing. After a selected number of echosignals 405, 409, 413, 417 are received, the characteristics of the echosignals 405, 409, 413, 417 may be processed simultaneously to provide animage based on all of the received signals. In this way, therotationally mounted radar, using a single radar sensor, acts similarlyto a radar system having a multiple sensor array. Due to the relativemotion and the resulting change in orientation between the radar sensorand the target 419, the rotationally mounted radar sensor provides aradar aperture that simulates the information obtained from multiple,spatially separated sensors.

Synthetic Aperture Radar (SAR) is a radar system that utilizes relativemotion between the radar sensor or antenna and the target. SAR usesmotion of the radar sensor relative to the target to take advantage ofthe Doppler history of the radar echoes generated by the motion of theradar sensor to synthesize or simulate a large antenna or antenna array.Inverse SAR (ISAR) uses relative motion of the target relative to astationary radar sensor in a similar manner. SAR allows for highresolution imaging using a physically small antenna. As the radar sensormoves, the radar signals are transmitted from varying positions. Thereturn echo signals pass through the radar receiver and are recorded inmemory. SAR requires precise location accuracy of the radar sensorduring transmitted radar signal. The contribution of each echo signalcorresponding to each transmit location is reconstructed and focused toimprove resolution significantly over real aperture radar (RAR). Therelative velocities between the radar transmitter and the targetreflector create Doppler shifts in the stored echo signals. The echosignals are processed according to their Doppler shifts to produce anarrow antenna beamwidth without the need for a physically long antenna.

ISAR is frequently utilized in maritime surveillance for theclassification of ships and other objects. An object on water is subjectto motion due the wave action of the water in which it is suspended. Forexample, a ship in water may have a physical feature, like a mast thatproduces a sinusoidal response to a radar signal that is clearlyidentifiable in a ISAR image. As the ships rocks toward and away fromthe radar sensor, an alternating Doppler response is returned. Attemptshave been made to adapt ISAR to ground based radar. However, there isdifficulty in utilizing ISAR in ground based applications because theobject motion is generally far less in magnitude and less periodic thatobject motion in the maritime scenario.

A radar system having rotationally mounted sensors effectively define aSAR system in which the rotational motion of the sensors (e.g. sensorsmounted on the blades of a wind turbine) define a sinusoidal, periodicresponse having magnitude even greater than a typical maritime target.The regular circular motion of the sensors provide an alternatingpositive and negative Doppler return as the blades alternately movetoward and away from the target. Unlike conventional SAR systems thatare mounted on an aircraft or a spacecraft such as a satellite, aground-based rotationally mounted radar sensor provides a prioriknowledge of the precise location of the sensor at any given time. Whenthe precise position of the radar sensors is subject to wind inducedturbine blade flex, the position accuracy can be further refined by anInertial Motion Unit (IMU) co-located with the sensor. Due to the largesize of wind turbine structures, a SAR system may provide a very largeeffective aperture size. For example, a wind turbine having a tower at120 meters and a blade length of 99 meters, defines a sweep area of 1.9acres. Utilizing multiple radar sensors across multiple blades, animmense effective aperture may be simulated compared to traditionalphased array antennas. In addition to the gains in effective aperture,the wind turbine described above provides an elevation of 219 metersproviding a substantial improvement in line of sight compared withconventional surveillance radar towers which may extend vertically about10-15 meters.

FIG. 5 is a process diagram depicting a method 500 for operating arotationally mounted radar system. A radar sensor is mounted to arotating structure. For example, the radar sensor may be mounted to ablade of a wind turbine. The radar sensor may be housed in a radomeaffixed to the blade tip of the wind turbine blade. In addition to orinstead of the blade tip, the radar sensor may be mounted at anyposition along the blade of the wind turbine that provides a rotationalmotion of the sensor as the blade turns. For example, one or more radarsensors may be disposed on the exterior surface of a blade along itsleading edge. The sensor transmits radar signals and receives echosignals of the transmitted signals that are reflected off of potentialtarget objects 501. As the sensor moves rotationally over time, the echosignals received by the sensor at a selected time interval are stored ina memory 503. The stored echo signals are analyzed and processed basedon characteristics of the received echo signals 505. By way ofnon-limiting example, characteristics such as amplitude, phase,polarization and the time the echo was received may be included in thesignal processing. Based on the processing of the received echo signals,an image of a potential target object is generated 509. Alternatively,the echo signals may be used to render a radar display in a map layout507. The map may include echo signal data that represents a potentialtarget. The map layout radar display may be configured to allow a userto select a potential target for imaging 508. Thus, the rotating sensorsmay be configured to provide surveillance and target imagingfunctionality. The stored echo signals are correlated and differencesbetween the stored signals are utilized to generate a high resolutionimage or display 511. For example, SAR processing may be used togenerate the image. The generated image is sent to a display or storagedevice according to conventional communication techniques to displayand/or store the generated image. It is to be understood that suchsignal processing and imaging and display capabilities may be extendedto other modes as described herein, such as for example, weatherdisplay, wind sheer GMTI, maritime modes such as oil slick detection anddrift, and the like. Such extension further includes one or moreintegrated electro-optical systems (EOS) such as a telescoping systemthat may be mounted on a structure such as a tower head, by way ofnon-limiting example.

In an embodiment of a rotationally mounted radar system, the controlcircuitry and processing of the radar system may be powered throughelectrical power produced from a wind turbine on which the radar systemis mounted. This provides a renewable energy source for powering theradar system and eliminates the need for transporting fuel to a radarinstallation, especially where access to the radar system may belimited. For example, the logistics of transporting fuel such as dieselfuel to power generators at remote surveillance locations is troublesomebecause of the cost in transportation as well as the difficulty inreaching the site where access roads may not exist. Providing power forthe system directly from the rotational mounting structure eliminatesthe need to limit placement of the radar installation due to theproblems involved in providing reliable power to the radar system.

FIG. 6 is a perspective view shown in phantom of an embodiment of radarsystem 600 rotationally mounted on a wind turbine. The wind turbine ismounted on a mast 105 which supports the nacelle 106. The nacelle 106provides a housing which contains the mechanical and control machineryfor the wind turbine and the radar system 600. The wind turbine hasthree blades 107, each blade having a radome 201 affixed at its tip. Theradome contains a radar sensor that transmits and/or receives radarsignals. The sensor is in electrical communication with the radarcontrol and processing circuitry 611 through a communication cable 205or other suitable link. The control and processing circuitry includesone or more processors and memory for transmitting and/or receivingsignal data and processing the data using SAR and ISAR algorithms andtechniques for performing threat detection and target discrimination byobtaining three dimensional imaging. The blades 107, when acted on byforce generated by air movements flowing past the blades 107, rotateabout an axis that is aligned substantially along the longitudinal axisof the nacelle 106. The rotational energy of the turning blades istransmitted through a torque shaft 601 which is further coupled to agenerator 603.

The wind turbine includes a controller 605 which provides control of theoperation of the wind turbine. For example, the controller 605 mayreceive input data from a wind vane or anemometer (not shown) todetermine the direction or speed of the prevailing winds. Based on theinput data, the controller 605 generates a control signal that istransmitted to an actuator that may control the pitch of the blades 107as indicated by arrow 607. The controller 605 may also generate acontrol signal that controls an actuator that provides yaw by rotatingthe nacelle 106 about mast 105 as indicated by arrow 609. Controller 605includes a processor configured for receiving input from components ofthe wind turbine and radar system and processing the inputs to providecontrol signals that are operative to control aspects of the radarsystem, such as transmit and receive power, image generation, signalprocessing of echo signals received by the radar sensor and otherfunctions known in the art used to operate a wind turbine and/or radarsystem.

The function of generator 603 is to generate electric power from therotation of the blades 107 resulting from force applied by the wind.This creates a sustainable source of green energy. Radar is a powercentric application, characterized by the fact that when power to theradar is increased, the effective range of the radar is also increased.A ground based radar system may consume power of about 10 kiloWatts (kW)to about 100 kW. A large wind turbine is capable of generating electricpower of more than 100 kW. Thus, a radar system rotationally mounted ona wind turbine may be power independent. When wind conditions are suchthat the wind turbine is unable to generate power from the force of thewind, backup power systems may be provided to keep the radar systemoperational. For example, battery power may be used to position theblades and attached radar sensors in azimuth by controlling the yawcontrol 609 actuator. Alternatively, the auxiliary power may providerotation of the blades 107 when the current wind conditions are notsufficient to provide rotation. In addition or as an alternative tobattery power, the wind turbine and radar system may be connected to apower distribution grid which may provide power for blade rotation oryaw control during times of poor wind conditions. The auxiliary powerfeature may also be used to selectively position the turbine bladesperpendicular to the wind direction, for the benefit of imaging a targetat the expense, at least temporarily, of generating power.

The radar control and processing circuitry 611 may be electricallycoupled 613 to generator 603 and configured to receive electrical powerfor generating radar signals via the rotationally mounted sensors, andfor powering processing circuitry for processing received signals andproviding imaging data based on the received signals. The blades 107rotate providing rotational movement of radomes 201 and the radarsensors housed therein. The radar sensors transmit radar signals as theyrotate and receive echo signals from target objects which impinge on thetransmitted radar signals. The echo signal data is stored in memory. Forexample, the echo signal data may be stored in a memory integrated aspart of radar control and processing circuitry 611. In oneconfiguration, a rotary joint (not shown) is disposed between the radarsensors on blade 107 and processing circuitry 611. The rotary jointpermits the blade assembly to rotate while transmitting power from thecontrol circuitry to the radar sensors via the blade 107, and provides apath for signals received by the sensor to be provided to the processingcircuitry. The rotary joint may include conductive brushes which conductelectrical energy received from a source node to a target node via anassociated rotating conductive surface disposed within the torque shaft601 which is in contact with the at least one of the brushes. By way ofnon-limiting example, the rotary joint and brushes may be configured toprovide one or more of power and high frequency communications data(e.g. via 802.11 protocol). Power may be transmitted from the turbinehousing to the blades as well as radio based signals to transmit highfrequency control and radar signals to/from the blades to the radarcontrol and processing circuitry. The stored echo signal data isprocessed, for example, the echo signal data may be processed as SARdata, to generate imaging data of the target object. The generated imageis then sent to a display or storage device which may be remote from thewind turbine. The generated image of the target object may then beviewed on a remote display or retrieved from memory and viewed at alater time.

According to an embodiment of a rotationally mounted radar system, acomplement of different frequency radar signals may be utilized toprovide simultaneously imaging, weather and surveillance capabilities.Higher frequencies provide better results for imaging or weather relatedradar applications. Lower frequencies provide greater range per unit ofpower consumed for surveillance applications. Referring again to FIG.2A, radome 201 a may be configured to house a radar sensor thattransmits radar signals in the X-band. Radome 201 b may be configured totransmit radar signals in a second frequency band. For example, radome201 b may house a radar sensor that transmits radar signals in theKu-band. Radome 201 c may house a radar sensor configured to transmitradar signals in the L, S, or C band. By utilizing complementary radarfrequencies, the coverage of the radar installation is maximizedproviding simultaneous imaging and surveillance.

In addition to mounting radar sensors on rotating blades at their tips,multiple radar sensors may be mounted at multiple positions along thelength of the rotating blade. This arrangement increases the number ofviewing angles for a particular target objects and provides thecapability to process a 3-dimensional image of the target object.Through 3-dimensional integration of echo signals received from multiplelocations, the resolution achievable extends beyond the fidelity ofimages generated through ISAR/SAR. To provide 3-dimensional imagingcapabilities, multiple radar sensors may be installed on multipleturbine blades in an integrated manner. This results in a syntheticaperture having a size defined by the entire sweep area of the blades asopposed to the swept arc defined by the path of the blade tips. Higherresolution imaging in this manner provides increased abilities forthreat detection. For example, a large target object detected travellingat 500 knots is probably an airplane, but a small object traveling atthat speed without a transponder is more likely a missile. The variationin perspective provided by the varying positioned radar sensors mayprovide further identification advantages. For example, a detectedobject may be discerned as a lone aircraft or a formation of aircraftbased on the ability to view the object from varying perspectives. Thus,there is disclosed a rotatably mounted radar system comprises a windturbine having a hub and a plurality of blades extending therefrom; aradar antenna configured to transmit and/or receive a radio frequency(RF) signal; and a processor in electrical communication with the radarantenna and configured to generate the RF signal for transmission and/orto process the received RF signal; wherein the radar antenna is affixedto one of the plurality of blades of the wind turbine such that relativemotion is defined between the radar antenna and a target within a lineof sight of the radar antenna.

Thus, there has been disclosed a blade mounted radar system comprising:a wind turbine having a hub and a plurality of blades extendingtherefrom; a radar antenna configured to transmit and/or receive a radiofrequency (RF) signal; and a processor in electrical communication withthe radar antenna and configured to generate the RF signal fortransmission and/or to process the received RF signal; wherein the radarantenna is affixed to one of the plurality of blades of the wind turbinesuch that relative motion is defined between the radar antenna and atarget within a line of sight of the radar antenna. In an embodiment, asecond radar antenna may be configured to transmit and receive an RFsignal, wherein the second radar antenna is mounted to a second one ofthe plurality of blades of the wind turbine. The first radar antenna maybe configured to transmit and/or receive an RF signal at a firstfrequency, and the second radar antenna may be configured to transmitand/or receive an RF signal at a second frequency different from thefirst frequency. A generator may be coupled to the wind turbine andconfigured to generate electric power, wherein the generator iselectrically coupled to the processor and configured to provide power tooperate the processor. In one embodiment, the generator may beconfigured to generate electric power between about 10 kiloWatts (kW)and about 100 kW. In one embodiment the first radar antenna may beconfigured to operate in X frequency band, and the second radar antennamay be configured to operate in Ku frequency band. Each of the first andsecond radar antennas may be affixed at a distal end of thecorresponding blade relative to the hub.

Further embodiments of the present invention disclose a methodcomprising: affixing at least one radar antenna to a corresponding oneof a plurality of blades of a wind turbine having a hub and with theplurality of blades extending therefrom; the radar antenna configured totransmit and/or receive a radio frequency (RF) signal; and processingradar signals transmitted and/or received via the radar antenna fordetecting an airborne target; the radar antenna being affixed to the oneof the plurality of blades of the wind turbine such that relative motionis defined between the radar antenna and the target within a line ofsight of the radar antenna. The radar antenna may be affixed at a distalend of the corresponding blade relative to the hub. In one embodimentthe step of affixing at least one radar antenna to a corresponding oneof the plurality of blades of the wind turbine comprises affixing to adistal end of one of the plurality of blades a first radar antennaconfigured to operate in a first frequency band, and affixing to adistal end of another of the plurality of blades a second radar antennaconfigured to operate in a second frequency band different from thefirst frequency band. In one embodiment, the first frequency band is theX frequency band, and the second frequency band is the Ku frequencyband.

Further embodiments of the present invention disclose a radar windturbine apparatus comprising: an electric generator in electricalcommunication with a power grid associated with the wind turbine; atorque shaft extending from a rotor of the electric generator; a bladeassembly coupled to the torque shaft, the blade assembly comprising: acentral hub comprising a rotational joint, the hub coupled to the torqueshaft; a plurality of blades, each blade coupled to the central hub; andat least one radar sensor disposed on or in one of the plurality ofblades. The apparatus further comprises a controller configured tocontrol operation of the wind turbine, where the controller is incommunication with the at least one radar sensor via the rotationaljoint in the torque shaft, and wherein the at least one radar sensorincludes an antenna configured to send and/or receive a radar signalbased on commands received from the controller. In one embodiment atleast two radar sensors are disposed on one or more of the plurality ofblades, wherein a first radar sensor is configured to send and/orreceive radar signals in a first radar band, and a second radar sensoris configured to send and/or receive radar signals in a second radarband different from the first radar band. In one embodiment the firstradar band is S-band Doppler radar for detecting weather, and the secondradar band is Ku band for detecting wind shear. In one embodiment thefirst radar band is configured to provide radar surveillance, and thesecond radar band is configured to detect weather. The controller may beconfigured to be in communication with the power grid. The power gridmay comprise at least one other power source, wherein if the windturbine detects an approaching severe weather event, the controller isconfigured to provide a signal to the power grid indicative of theweather event and of measures to secure the wind turbine. The signalprovided to the power grid may include an instruction to increase poweroutput from the at least one other power source. The measures to securethe wind turbine may include slowing a rotation of the blade assemblyand/or turning the blade assembly to a direction relative to aprevailing wind direction. In one embodiment, the first radar band isconfigured to provide radar surveillance and the second radar band isconfigured to provide radar imaging. In an embodiment, the radar imagingis performed on a selected target, the target selected by a user basedon a map display of information based on the radar surveillance. Atleast one radome may be disposed at a tip of one of the plurality ofblades, with at least one radar sensor housed within the at least oneradome. In one embodiment, at least one radar sensor is disposed on anexterior surface of one of the plurality of blades. The at least oneradar sensor may be disposed on a leading edge of the blade.

While the foregoing invention has been described with reference to theabove-described embodiments, various modifications and changes can bemade without departing from the spirit of the invention. For example,while embodiments of the invention illustrate a radar dome on a givenblade tip of a wind turbine, such embodiments may be extended to includeone or more radar antenna phased arrays and/or line array panelsextending from the tip of the blade toward the center to a givenspecified length. Such structures may be configured with or without adome, as conformal arrays (e.g. taking the shape of the blade on thetip), and the like. Furthermore, different frequency bands or radartypes may be integrated into or on the different blade-tips. Such radarconfigurations may include X-band imaging type radar for primaryISAR/SAR imaging functions while implementing an L, S, or C Band radarfor another tip that would primarily gain the elevation LOS forsurveillance modes. Such may be configured without utilizing SAR butrather an adapted Doppler for weather functions. Accordingly, all suchmodifications and changes are considered to be within the scope of theappended claims. Accordingly, the specification and the drawings are tobe regarded in an illustrative rather than a restrictive sense. Theaccompanying drawings that form a part hereof, show by way ofillustration, and not of limitation, specific embodiments in which thesubject matter may be practiced. The embodiments illustrated aredescribed in sufficient detail to enable those skilled in the art topractice the teachings disclosed herein. Other embodiments may beutilized and derived therefrom, such that structural and logicalsubstitutions and changes may be made without departing from the scopeof this disclosure. This Detailed Description, therefore, is not to betaken in a limiting sense, and the scope of various embodiments isdefined only by the appended claims, along with the full range ofequivalents to which such claims are entitled.

Such embodiments of the inventive subject matter may be referred toherein, individually and/or collectively, by the term “invention” merelyfor convenience and without intending to voluntarily limit the scope ofthis application to any single invention or inventive concept if morethan one is in fact disclosed. Thus, although specific embodiments havebeen illustrated and described herein, it should be appreciated that anyarrangement calculated to achieve the same purpose may be substitutedfor the specific embodiments shown. This disclosure is intended to coverany and all adaptations of variations of various embodiments.Combinations of the above embodiments, and other embodiments notspecifically described herein, will be apparent to those of skill in theart upon reviewing the above description.

What is claimed is:
 1. A blade mounted radar system comprising: a wind turbine having a hub and a plurality of blades extending therefrom; a radar antenna configured to transmit and/or receive a radio frequency (RF) signal; and a processor in electrical communication with said radar antenna and configured to generate the RF signal for transmission and/or to process the received RF signal; wherein said radar antenna is affixed to one of the plurality of blades of the wind turbine such that relative motion is defined between said radar antenna and a target within a line of sight of said radar antenna.
 2. The system of claim 1, further comprising: a second radar antenna configured to transmit and receive an RF signal, wherein said second radar antenna is mounted to a second one of said plurality of blades of said wind turbine.
 3. The system of claim 2, wherein said first radar antenna is configured to transmit and/or receive an RF signal at a first frequency, and said second radar antenna is configured to transmit and/or receive an RF signal at a second frequency different from said first frequency.
 4. The system of claim 1 further comprising: a generator coupled to said wind turbine and configured to generate electric power; wherein said generator is electrically coupled to said processor and configured to provide power to operate said processor.
 5. The system of claim 4, wherein said generator is configured to generate electric power between about 10 kiloWatts (kW) and about 100 kW.
 6. The system of claim 2, wherein said first radar antenna is configured to operate in X frequency band, and said second radar antenna is configured to operate in Ku frequency band.
 7. The system of claim 2, wherein each of said first and second radar antennas is affixed at a distal end of the corresponding blade relative to the hub.
 8. A method comprising: affixing at least one radar antenna to a corresponding one of a plurality of blades of a wind turbine having a hub and with said plurality of blades extending therefrom; the radar antenna configured to transmit and/or receive a radio frequency (RF) signal; and processing radar signals transmitted and/or received via said radar antenna for detecting an airborne target; said radar antenna being affixed to said one of the plurality of blades of the wind turbine such that relative motion is defined between said radar antenna and said target within a line of sight of said radar antenna.
 9. The method of claim 8, wherein said radar antenna is affixed at a distal end of the corresponding blade relative to the hub.
 10. The method of claim 8, wherein the step of affixing at least one radar antenna to a corresponding one of the plurality of blades of the wind turbine comprises affixing to a distal end of one of said plurality of blades a first radar antenna configured to operate in a first frequency band, and affixing to a distal end of another of said plurality of blades a second radar antenna configured to operate in a second frequency band different from said first frequency band.
 11. The method of claim 10, wherein said first frequency band is the X frequency band, and said second frequency band is the Ku frequency band.
 12. A radar wind turbine apparatus comprising: an electric generator in electrical communication with a power grid associated with the wind turbine; a torque shaft extending from a rotor of said electric generator; a blade assembly coupled to said torque shaft, said blade assembly comprising: a central hub comprising a rotational joint, said hub coupled to said torque shaft; a plurality of blades, each blade coupled to said central hub; and at least one radar sensor disposed on or in one of said plurality of blades.
 13. The apparatus of claim 12, further comprising: a controller configured to control operation of said wind turbine, said controller in communication with the at least one radar sensor via said rotational joint in said torque shaft, wherein said at least one radar sensor includes an antenna configured to send and/or receive a radar signal based on commands received from said controller.
 14. The apparatus of claim 13, further comprising at least two radar sensors disposed on one or more of said plurality of blades, wherein a first radar sensor is configured to send and/or receive radar signals in a first radar band, and a second radar sensor is configured to send and/or receive radar signals in a second radar band different from said first radar band.
 15. The apparatus of claim 14, wherein said first radar band is S-band Doppler radar for detecting weather, and said second radar band is Ku band for detecting wind shear.
 16. The apparatus of claim 14, wherein said first radar band is configured to provide radar surveillance, and said second radar band is configured to detect weather.
 17. The apparatus of claim 16, wherein said controller is in communication with said power grid, wherein said power grid comprises at least one other power source, and wherein if the wind turbine detects an approaching severe weather event, said controller is configured to provide a signal to said power grid indicative of the weather event and of measures to secure said wind turbine.
 18. The apparatus of claim 17, wherein the signal provided to the power grid includes an instruction to increase power output from the at least one other power source.
 19. The apparatus of claim 17, wherein said measures to secure said wind turbine include slowing a rotation of said blade assembly and/or turning said blade assembly to a direction relative to a prevailing wind direction.
 20. The apparatus of claim 14, wherein said first radar band is configured to provide radar surveillance and said second radar band is configured to provide radar imaging.
 21. The apparatus of claim 20, wherein said radar imaging is performed on a selected target, said target selected by a user based on a map display of information based on the radar surveillance.
 22. The apparatus of claim 12, further comprising at least one radome, said radome disposed at a tip of one of said plurality of blades, said at least one radar sensor being housed within said at least one radome.
 23. The apparatus of claim 12, wherein said at least one radar sensor is disposed on an exterior surface of one of said plurality of blades.
 24. The apparatus of claim 23, wherein said at least one radar sensor is disposed on a leading edge of said blade. 